Electric furnace.



1. RENNERF BLEG 0 FURN APPLIGATIO I ED FEB. 26, 1912.

1,076,518. Patented 001;. 21, 1913.

UNITED STATES IVAB RENNERFELT, 0F HALMSTAD, SWEDEN.

ELECTRIC FURNACE.

Specification of Letters Patent.

Patented Oct. 21, 1913.

Application filed February 26, 1912. Serial No. 680,003.

To all whom, it may concern:

Be it known that I, lvAR R NNERFELT, a subject of'the King of Sweden,and a resident of Halmstad, in the county of Halland and Kingdom ofSweden, have invented certain new and useful Improvements in ElectricFurnaces, of whichthe following is a specification.

My invention relates to improvements in electric furnaces in which theheat is generated by means of arcs and the objects of my invention are:to provide means for changing of the vertical location of the source ofheat in the interior of the furnace at the will of the operator; toafford facilities for operating the furnace with arcs independent of thecharge or, if so desired, with arcs between the charge and theelectrodes; to afford an easy access to the interior by arranging theelectrodes and their supports so as to permit their Withdrawal entirelyfrom the openings 'in the walls made for the electrodes; to afi'ordmeans for an automatic stirring of the molten charge; to arrange theelectrodes in such a manner as to permit the operation of a furnace onany system of electric power supply, direct current or alternatingcurrent of any phase number or frequency; to facilitate smelting of coldscrap using power from small units of distribution, sensitive todisturbing influences regarding the voltage regulation; to build thesmelting crucible of an electric furnace so as to obtain a considerablemechanical strength at the same time utilizing as much of the energysupplied as possible. I gain these objects by arranging the electricfurnace as illustrated in the accompanying drawing in which Figure 1 isa vertical section of a furnace with electrodes arranged in a horizontalo.- sition as well as vertical or rather r ial position. Fig. 2 is asectional view of the furnace in Fig. 1 on the line w-.'1:. Fig.3 is avertical, part sectional, part side view of a furnace having horizontalelectrodes which may be tilted in different angles,

whereas those of Figs. land 2 are intended to be adjusted vertically bymoving the el e trodes transversely to t elr axls ma ntamlng the samealways parallel to its original location. a

The radial electrode may be omitted in case'of using direct or singlephase current but it may also be connected to the neutral wire in a3-wire system or it may be used with single phase current taking the sumof the currents in the end electrodes. On polyphase systems, which aretransformed to twophase current, if the power suppl is .threephasecurrent, said radial electr e. is

to be connected to the middle point of the secondar of the twophasetransformer and.

carries ,t e geometrically resulting current of the components in thetwo phases. 7

Throughout the several views similar parts are'indicated by similarletters of reference. 1

The smelting hearth of the furnace has the shape of a cylindricalcrucible 1, resting on rollers 2 so as to be easily rotated fordischarge of slag and metal through thespout 3. The'charge of forinstance molten steel and slag is indicated by t. A projection 5 fromthe lower part of the crucible serves as means for stirring or mixingthe charge by rotating the crucible one way or the other.

The heat is enerated by means of arcs between the ralli'al electrode 6and more or less horizontal electrodes 7. The radial electrode islongitudinally adjustable but not otherwise. The, horizontal electrodesare supported by suitable means 8 permitting the raising or lowering ofthe electrodes according to where the arcs are wanted in the crucible.

a trolley 10 or. someother arrangement as for instance hydraulic orpneumatic lifts located on the round.

The radial e ectrode need not be electrically insulated but isprovidedwith cooling me ium by means of a waterjacket 11. The

horizontal electrodes are cooled by similar Waterjackets' 11 and wellinsulated electri- The means for said ad'ustment may be either ahoisting rope 9 rom.

cally' from each other and from the radial electrode.

Means for adjusting the length of the arcs are shown In 3 and consist ofa pipe 12 insulated from the cooling jacket by means of aacking 13 ofasbestos or similar material. nside of the pipe is an elastic packing ofcopper gauze 14. making a slidin contact w1th the electrode with enoughfrictional resistance to cause the electrode to follow the movement ofthe pipe in or out. 'Said movement is caused by any approved means,suchas a screw, a hydraulic plunger ing pendent on the drawing.

the pipe and the pac of this is sinking down when being sme cylindricallinin or other suitable arrangements not indicated The current isconducted by means of clamps 15, on pipe surrounding same;

ing between it and the electrode-is of copper or other conductingmaterial. The horizontal electrodes of Fig. 3 are supported ontrunnionsor journals 16 permitting an angular movement of the electrode around anaxis located at right angle to the longitudinal axis of the electrode.The electrode is protected from the furnace heat by highly refractorymaterial supported by the trunnions 16 and moving with the electrode.

By giving the end electrodes of'Fig. 1 a suitable inclination toward thecharge and then lowering them close enough to the surface of the chargetogether wlth the radial electrode,

to the electrode the electrode or the if. such be used, it becomespossible to heat the bath'directly by arcs operaton the charge itselfmaking same part of the path of the current. The same mode of operationis attained in Fig. 3 by tilting the electrodes sufliciently. It isclear that this highly facilitates the operation of the furnace on coldscrap: Such a charge offers a much varying resistance to the current, ifthe arcs are playing on the scrap, causing bad short circuits veryfrequently with difliculties in maintaining a smooth service. It isbetter, then, to use arcs indeof the charge, as long as it has notbecome molten and to send the current through the charge, only after abath of fluid'm'etal and slag has been obtained. It is possible tocharge more scrap into a furnace, where the electrodes may be located aproper distance above the top of the charge and to maintain a minimum ofdistance between the arcs and the charge, as the tpp ed. In this way thehighest efliciency will always be maintained. The cylindrical shape ofthe crucible not only gives to the walls and roof a high degree ofmechanical stren .h but also serves to save energy as part of the heatwhich is radiated upward is reflected down to the surface of the charge.Another part of the heat absorbed by the walls may be recovered bytilting the crucibleso as to bring the charge into contact with theheated walls thereby absorbing some of the heat. The maintenance of afurnace of this character is relatively cheap as a new may be rammedinto the crucible at smal cost with a minimum of time, labor andmaterial.

Having now fully described my invention side of the crucible means of ashield 17 of Stockholm and-- I claim and ,desire to secure by LettersPat ent of the United States of America:

1. In an electric furnace the combination of a crucible arranged to berotated around a horizontal axis, electrodes projected into the cruciblefrom opposite sides, another electrode projected vertically through theinto close proximity to the inner ends of the first said electrodes andmeans for adjusting the relative distance between the three inner endsof all the electrodes, the electrodes bein so arranged that an arc isestablished from the vertical electrode to each of the other electrodes.

2. In an electric furnace the combination of a crucible arranged to berotated around a horizontal axis, a shield at each end of the crucible,an electrode extending through each shield, another electrode extendingin radial direction through the wall of the crucible, and means foradjusting the shields in vertical direction.

3. In an electric furnace the combination of a crucible arranged to berotated around a horizontal axis, an electrode through each end of thecrucible, another electrode extending vertically through the side of thecrucible into close proximity to the inner ends of the first saidelectrodes and means for adjusting the relative 'distance between thethree inner ends of all the electrodes, the electrodes being so arrangedthat an arc is established from the vertical electrode to each of theother electrodes.

4:- In an electric ofa crucible arranged to be rotated around ahorizontal axis, an electrode through each end of the crucible, anotherelectrode extending vertically through the side of the crucible intoclose proximity to the inner ends of the first said electrodes, meansfor adjustin the relative distance between the three lnner ends ofallthe electrodes, the electrodes being so arranged that an arc isestablished from the vertical electrode to each of the other electrodesandmeans for rotating the crucible so as to vary the distance betweenthe ends ofthe electrodes and the surface of the molten charge withinthe crucible.

Signed at Stockholm in the county of the Kingdom of Sweden this 30th dayof January A. D. 1912.

IVAR RENNERFELT.

furnace the combination

